Idle Advance Control Valve (IACV) on Throttle Body - Miata Turbo Forum - Boost cars, acquire cats.

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Old 04-28-2012, 06:16 PM   #1
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Default Idle Advance Control Valve (IACV) on Throttle Body

Anyone ever fiddled with removing, capping off or closing the loop of the IACV, located at the bottom of the throttle body? I know that with a MS unit the idle can be controlled, but don't know what kind of hell I'd get in by simply disconnecting the unit.

Is it for cold start or emissions only?
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Old 04-28-2012, 06:31 PM   #2
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Just disconnect the connector and see how you like it...
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Old 04-28-2012, 06:34 PM   #3
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If the car is driven on the street, you really want to keep the idle valve. Theseus doesn't have one, but it idles at 1200rpm without the fan on and ~1000rpm with the fan on.
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Old 04-28-2012, 06:43 PM   #4
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Why not just set the maximum value to 0 or disconnect it and be done with it?

Extra juice when the alternator kicks on, AC, cold starts, initial starts, hot idle/fans kicking on.. In all those the IAC helps stabilize the extra load/rpm.
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Old 04-28-2012, 07:12 PM   #5
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My reason for asking...I've got a 70mm throttle body that's intended for a Honda. I want to do some testing with it, and didn't know what type of variables to expect. It's going on a 1999 with AC and PS delete.

I'm curious more than anything to see how the car will respond to the throttle body on cars in various states of modification. First step, mostly stock.
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Old 04-28-2012, 07:18 PM   #6
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Why not control the honda iidle valve...
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Old 04-28-2012, 07:36 PM   #7
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Quote:
Originally Posted by Braineack View Post
Why not control the honda idle valve...
That's on the list. I simply don't want to reproduce a tangle of lines that may have been put there by Uncle Sam.
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Old 04-28-2012, 09:13 PM   #8
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are you talking about the coolant lines?
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Old 04-28-2012, 09:26 PM   #9
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Quote:
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are you talking about the coolant lines?
Well the hyper reroute would take care of those.
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Old 04-28-2012, 09:37 PM   #10
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Ka-slam!
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Old 04-28-2012, 10:35 PM   #11
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Quote:
Originally Posted by Braineack View Post
are you talking about the coolant lines?
Them are the ones I'm talking about. I have this frustrating habit of questioning the value of everything on the car--is it really needed? Can it be made better, lighter, etceteras. I can understand not wanting the idle to hunt when using the A/C, but the A/C is long gone. And if I'm doing all of this for the gubmint, then I'd just as soon NOT.

I'm rebuilding a 1977 Chevy Blazer, and have put a more efficient, cleaner fuel injected engine in it. California is going to make me jump through hoops to register because it doesn't see the pre-heater hose going from the header to the carburetor, or other vacuum lines that are no longer required. I'm installing catalytic converters (2) as well, but they probably won't be the kind that are mandated. Cleaner, more efficient, quieter, illegal.
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Old 04-28-2012, 11:42 PM   #12
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Pull them and forget.
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Old 04-29-2012, 01:25 AM   #13
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Quote:
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Pull them and forget.

YES! That's what I wanted to hear. Thank you Mr. Brain...
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Old 04-29-2012, 05:39 PM   #14
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You can pull the coolant lines off without any ill effect, but if you just remove the entire idle valve and cap it off, driveability will suffer.
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Old 06-20-2012, 05:15 PM   #15
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Bumping this older thread.


What do you think of the complete removal of the iacv for a track-only car?
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Old 06-20-2012, 05:21 PM   #16
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Quote:
Originally Posted by shlammed View Post
Bumping this older thread.


What do you think of the complete removal of the iacv for a track-only car?
Why would you want to remove it even for race application? 2oz weight reduction?
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Old 06-20-2012, 05:30 PM   #17
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My first Miata idled better with no IACV and no AC than my current one does with AC and the stock IACV controlled by an MSPNP.

You'd play hell trying to keep the thing lit with AC and no IACV, but without either, I wouldn't sweat it. I didn't notice any significant idle change when the fans kicked on/ alternator load changed, btw. It was rock solid 900-1000 rpm pretty much all the time.
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Old 06-20-2012, 05:48 PM   #18
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I just finally connected my idle control valve after 1.5 years and 16000 miles of driving without one.
I ran it purely on the idle screw and ~950-1000rpm idle. No AC or PS.

Only had issues with idle after it sat outside in freezing temperatures for a week. The fix for that was to just hold the throttle for a minute and then it was able to idle.

So in my opinion it is completely optional.
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Old 06-20-2012, 05:57 PM   #19
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How about when fans turn on, or you raise the windows and all that? Track car sure no windows but still have the fans.
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Old 06-20-2012, 06:00 PM   #20
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Fans had no appreciable effect on my car, and it had roll up windows.
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